In the production of hydrocarbons from producing formations, it has become common to drill directional wells from the earth's surface to an underground producing formation. Directional drilling usually involves diverting a well from the vertical at some place below the earth's surface to direct it to a remote producing formation. The directional or slanted wells may deviate up to 90.degree. from the vertical to reach a desired producing formation.
The directional wells are completed for the production of hydrocarbons using suitable casing strings and production liners. It is often desirable to remove or "clean out" material from directional wells during completion, recompletion or service operations on the wells. Heretofore, as noted in U.S. Pat. No. 3,463,231, a gas-liquid foam has been used to clean out wells. Foam cleanout has been done in directional wells. However, in wells having more than 15.degree. deviation and especially more than 30.degree. deviation from the vertical, it has been found that special techniques greatly improve the removal of material. The present invention is directed to improving foam clean out in such directional wells.